Unfortunately, while I'm currently levelling my DM/SR stalker, I can't really comment, as I've skipped Shadow Maul.
I skipped it because :
a) anything/SR is a stupidly tight build to start with.
b) I'm going for a fast cycling attack chain.
c) did I mention the stupidly tight build? I'm 35 and don't even have a travel power prerequisite yet.
d) I like the animations on the other powers, Shadow Maul less so.
I've not decided yet if I'm going to bother with a patron, since skipping the whole 'lackey of one of Recluse's paranoid moron lieutentants' thing on my Corruptor did nothing bad to her survivability, and frankly, there's nothing interesting enough in the PPP's to really grab my attention.
If I skip the PPP's, then I'll end up taking it eventually, but my picks up to about 44 are spoken for already... <sigh>
:edit: BTW, I'm going for a PvE only stalker play experience. PvP holds no attractions for me at all.
Warning:
The above post may contain Cynicism, sarcasm and/or pessimism. If you object to the quantities contained, then tough.
If you solo a lot, then Shadow maul is quite a nice attack to have. You can take that second to line up 2-3 mobs to hit them, its good for bosses and just when you want to get scrappy. Yes it has its downsides and is especially annoying when you miss, and yes, if you really are tight for space in your build, It is possible to skip it once you are past 32 and get the awesome MG. But I have it on my stalker, and like it...when it hits.
As for Patrons, I love my ranged blast and hold. A stalker with range and a hold is a scary thing, even in PvE.
I have a DM/SR stalker and have got shadow maul i find it rather good myself but most will disagree with some technical garbage about root times and whatever else. I play in pvp and pve with it and not had such a huge problem, if anything i skipped shadow punch (the first attack i maybe wrong with the name). But hey people use sands of mu and miss alot more than you would with shadow maul.
My general opinion is don't skip it as it has its uses, specialy if you can get the cone to hit the max targets your after.
Mines six slotted by the way which shows i like it.
One of the leaders of the Harlequins villain group and currently on defiant.
[ QUOTE ]
I have a DM/SR stalker and have got shadow maul i find it rather good myself but most will disagree with some technical garbage about root times and whatever else. I play in pvp and pve with it and not had such a huge problem, if anything i skipped shadow punch (the first attack i maybe wrong with the name). But hey people use sands of mu and miss alot more than you would with shadow maul.
My general opinion is don't skip it as it has its uses, specialy if you can get the cone to hit the max targets your after.
Mines six slotted by the way which shows i like it.
[/ QUOTE ]
I'm not saying I hate it or anything. I use Sands of Mu semi-regularly, but I like the rapid fire punch, punch, Steal portion of soul, summon tentacles of doom, punch, punch mobile style of play.
If anything, Shadow Maul would help my endurance situation, as the 3 second activation would be three seconds where I'm not burning end on rapid charging, even faster animating attacks 
:edit: I'm not trying to disparage anyone's choices. I'm just saying why I've not taken it yet. I'm trying, half heartedly, for a semi-buzzsaw build, and an attack as long as Shadow Maul doesn't fit that concept for me. SM's still a damn good attack, it's just not for my character concept and playstyle.
Warning:
The above post may contain Cynicism, sarcasm and/or pessimism. If you object to the quantities contained, then tough.
I've read a lot of hate aimed at Shadow Maul over my 6 months of CoX, particularly from Stalkers. Now, back in the day I could understand it... You were meant to play hit-and-run (well, mostly), so long-rooting attacks were just not good. Especially not in PvP, but let's not get too far into that. Also, Cones only have half-chance to crit from Hide, so you were more likely to use Smite or something after that Placate anyway, right?
However, two things spring to my mind.
1) That's not really that bad. Aside from 3 second root time equalling suicide in PvP, it doesn't seem to be a bad attack. One, it's the second hardest hitting non-AS attack in the set - a set that already had few attacks before being ported to Stalkers and gaining AS+Placate, trading them for utility powers like Touch of Fear (it's up to you if you count Siphon Life as an attack or a self-heal). In addition, it's a cone, which means you can reliably hit up to 3 targets with it, and in a theoretical best-case scenario, up to 5 targets. And all 5 of them will gain a modest ToHit debuff. Yikes! Also, assuming you don't miss and are not too much of a number cruncher to be that bothered by a 3 sec animation, it looks friggin' awesome.
2) I get the feeling that people are just easily frustrated by the power's tendency to REALLY show bad luck. When you miss with Shadow Punch, you hardly notice it - it's a quick attack and has a 3 second recharge. When you miss with Shadow Maul you look like a moron fanning the enemy to cool him down, for 3 seconds, unable to move or defend yourself. Getting some decent Accuracy easily solves this, although most people appear to spec it out ASAP because of how annoying this can be in lower levels.
Worse, the cone is actually very narrow. While those of us more experienced with the PITA that are melee cones (Flashing Steel doesn't count) are able to reliable hit 2-3 enemies with it per use, others will notice the poor recharge and endurance cost of a cone power when they only manage to hit one of the enemies. And it's even worse if they miss.
Also: In these modern times, Stalkers can arguably scrap better than scrappers. Would this power actually work in your builds now that Stalkers got those recent buffs, especially being able to crit out of hide? Keep in mind that AoEs and Cones get the same out-of-hide crit chance that Single Target attacks get, so in an 8-man team... Hmm.
Please, do share your thoughts. Shadow Maul - still garbage, or fun in PvE (with 3 Accuracy IOs if possible)?