Yeah that jives with my experience Mindzeye pretty well: I didn't know about the ally achievments until partway through the first story mission (Therum IIRC). Up until then I changed my squad around a bit but figured I'd just keep ash and liara since I didnt feel like constantly leveling up/equipping all the squad members.
Its a good thing I started using them exclusively when I did fairly early on (and perhaps even necessary that I did Wrex and Garrus' unique missions using ash and laira) because while I got the "soldier ally" ach a few missions before the end, I didn't get Asari Ally until right before the final boss fight. I was relieved b/c I did make it a point to do EVERY SINGLE SOLITARY side quest. I mean every friggin one! Even then I didn't get it until the near the very end, but that's probably b/c I switched squad mates a little during the beginning.
GENERAL TIP: You don't have to go out of your way to decrypt every probe or scan every mineral deposit. I ended up having a 9/6 gasses, 25/20 asari writings, 24/20 light metals etc. So they do give you some extra's in case you miss a couple. Roaming around in the mako looking for ore deposits to pop up on your radar was a pain in the ass and evidently unnecessary.
Some Overall Impressions (like any of you care), but you're obviously interested enough to be surfing the ME thread so I'll continue to act like you care:
1. The sidequests were pretty repetitive and many were downright IDENTICAL (I don't mean similar, I mean IDENTICAL) which was a turnoff but I'll use the same logic I did to cmoplaints about Ass Creed being repetitive: Repetitive sex with a hotgirl may be repetitive, but its still

in awesome!!
2. The story....wow, just wow. I've never been too into the Sci Fi genre but it just opens up so much story possibilities its mind boggling. The end was great and the Story missions and planets were really really fun and varied greatly. 10/10!
3. Graphics: Meh, Great but to be expected, Not the same quality as Gears or Bioshock but as good as or better than Halo. 8/10.
4. Replay value: Fantastic! I can't wait to get home and start my next playthrough as renegade, I'm really looking forward to being a bad ass after behaving well the first playthrough. 10/10.
5. Difficulty: Meh, unbalanced at best. Unbalanced in a very bad way in the beginning (you get owned) and unbalanced in a very good way at the end (you own). It had a perfect balance of difficulty for about 5 hours in the middle.
6. Achievment whore? THis game is for you, it will keep you coming back for more, it pretty much takes FOUR playthroughs, (at least 3.5) to get everyone. I had a lot of fun trying to get some achievments.
Misc. comments: The complete lack of tutorials really pissed me off. I mean comeon, I'm new here, I may be a hardcore gamer but I still need SOME (albeit very basic) direction, what button does what etc.... This sucked and was just a major

up IMO. The interplay between pure RPG elements and the 3rd Person shooter elments really worked well and much better than any other game I'v ever played.
OVERALL SCORE: 9/10. Room for improvement but a nice start! Way to go Bioware, its an improvement from both baldur's gates and KOTOR (Gotta assume this since I've never played KOTOR).