Sure, which is why I said in my first post on the subject:
Outlook is actually far more responsive even though my Outlook profile has a nearly 2GB OST.
Outlook 2010 is actually much improved here over previous versions, but it's hardly shocking that Outlook would be more demanding of resources, it's probably the most complete and full-featured email client on the planet.
But even with that in mind, I find that overall, even despite the massive difference in the quantity of email I have in my Outlook account - it actually performs better than WLM 2011, and that's with my prejudice of Outlook's reputation of a resource hog taken into account (believe me, Outlook 2003 on a first-month Vista system with a woefully unoptimized Norton? Sweet jeebus you don't know pain my son. )
It's not as if WLM is a POS, it certainly isn't - I keep trying Thunderbird and other free email clients, but with the combination of features/interface/syncing/offline capabilities, WLM is the best. It's just frustrating that it seems to demand resources far excess in what I think a relatively simple email client should. I am not exaggerating by comparison, that OSX's Mail app - a pretty decently featured email client in itself - launches and fetches mail an order of magnitude faster than WLM (or at lest, doesn't cripple the system while it's fetching mail). It's not as if WLM is managing some massively complex OST database either, it stores emails as single files like like OSX mail, and as mentioned I have less than 100MB total.
Perhaps it's not WLM though, perhaps this is something with NTFS, dunno - I was reminded of this today when I had to duplicate a 50 GB VM file to another folder on my desktop, which admittedly is not a screamer (X2 215 2.7ghz, 4GB ram, 1TB 7200 RPM drive) - but not a slouch either. While that file was copying, my system basically slowed to a crawl (and no, the drives were not in PIO mode). This is not a unique experience, I generally find that Windows just hits the damn HD so, so bloody damn often for common tasks. You should NOT see the "work in progress" spin icon when just right-clicking on the desktop for pete's sake, even for a split second.
I've done the same on OSX - on a old Macbook with a 5400rpm notebook drive, and while the performance hit is definitely palpable, it's not system-crippling like it is on Win7/Vista. I've been installing Office on that thing (which on the Mac, basically involves a straight dump of files from one folder to another) and barely notice the hit when performing common tasks.
Even browsing and scrolling was significantly affected while this straight copy job is going on with my Win7 PC, and it's not just this system - outside of SSD equipped systems, I've found this universal across XP/Vista/Win7 and high I/O loads. Something in the way Windows handles apps with high I/O seems to impact the overall system responsiveness more than other OS's it seems... but admittedly this is anecdotal. When I have access to my old mans iMac/Macbook I think I'll make a video for comparisons sake. Not to tout OSX as the perfect OS by any means, it certainly isn't - but user-interface responsiveness in the face of high I/O, in my (admittedly limited) experience, it has Win7 beat handily.
Oh, and during these experiences - no AV on my Win7 system (just to narrow it down as a culprit, I usually keep one running for at least examining Internet download activity, if not all read/write I/O).