I work for IBM in Rochester, MN. I'm a performance analyst for WebSphere App Server (some of the geeks may have heard of it.. for the rest it's just an application server.. we're running more and more of ebay every day). Bottom line.. I think whatever study came to that conclusion had to be horribly wrong in some of their methodology. Ingenuiti already pointed out the Fortune surveys, and from a perspective of benefits and features IBM deserves those ratings.
It may be my perspective, so here's a little rundown. I graduated from college with a bachelor's degree in May of 2002 and started here immediately. Think about May of 2002 for a second and the state the industry was in. I'm serious.. it was the ONLY interview I had. Period. They could've capitalized on the situation and low balled me because they knew I wouldn't be able to get anything better, but they didn't. I got the exact same offer as a friend who had been hired a year and a half before, even adjusted for inflation. Beyond that, the salary was highest in my entire circle of friends graduating at the time. (This isn't dick wagging... I'm trying to back up my point) Also I've gotten no less than two separate raises since then totaling and increase of 15% in 18 months. In addition, there are variable bonus payouts based on business peformance and personal performance that have averaged out to about 7% each year I've been here. That's just from a sheer cash perspective. I get full medical coverage (copay, not deductible... although there's hints that may be changing unfortunately) for about $20 a month and when I'm married in June my fiancee will be only $80/mo for full coverage. Dental is free and I pay 9$/mo for almost complete vision coverage.
There's a billion and one internal programs for incentives to be healthy, learn, etc.. and if that isn't enough they'll assist you in pursuing that stuff outside the company. Right now I'm getting a masters degree 100% on their dime. I've got stock options that are going to fully comprise a sizable down payment on my house later this year.
I'll concede the point that some of this stuff is only if you bust your ass and work alot... but what's wrong with that? It's the freaking technology industry.. it's SUPPOSED to be that way. But 90% of that stuff is still applicable to anyone picking up a paycheck. In addition, they're committed to helping out even their low performers. Unless it's spurred by some major rule infraction, you will almost never see someone with less than 3 years in the company fired. They'll transfer you to get you the right fit of responsibility and skill. Hell.. it's a REQUIRED TASK to fill out a development plan that keeps you thinking about growing your skills over the next 5 years and giving concrete methods by which you'll reach those goals. I can take off whenever I want as long as the work is done, and they recently increased vacation for everyone by an entire week, so now I have three weeks of vacation PLUS 5 or 6 'personal choice holidays' depending on how the holiday schedule works out for a given year.
The only points I can think of that people may be harping on is the recent (5-7 years ago) change in pension plan which is quite a bit less lucrative than the old plan, but still above average, and the impending change in benefits.. namely the health coverage. I agree that those are important points, but hardly enough to make it one of the worst companies to work for. Bottom line is that in a company this big, there's so much infrastructure to keep you on your feet and so many programs and incentives provided through economies of scale that you almost have to TRY to fail.
Sorry this is so long but I sort of had to step up and figured since I work here it might be 'straight from the horses mouth'. Don't get me wrong.. i'm not a cheerleader or anything. I can only imagine myself here for 5 years or so, mostly because I'd like to advance faster than is possible here. (360,000 people all highly capable and many working in the exact same skill area causes alot of contention) In my opinion though, it's a great place to start a career and end a career. And if you're happy playing some of the political games and manuevering for highly contested positions, it's a high potential long haul company with constant safety nets.