Pros
They are building a good business and have good relationships with clients. If I needed tax preparation work, I'd probably use Andersen Tax, but I wouldn't ever work at a company like this. Life is too short for crappy employment!
Cons
My experience may be similar to other large accounting firms, but from speaking with my friends working at the Big4, I think my experiences at WTAS (now Andersen Tax) were substantially worse. Here's the gist of it: The firm didn't have a good process for copying tax returns so they asked every tax preparer to copy their own returns, get all the envelopes and "sign here" stickers placed, and put the copies in the nice packets. This process consistently took about 1 hour to do for a typical return. I spent 2 months perfecting the process until it took 22 minutes and I never had to walk over the same floor space twice. Then I presented what my improvements to managers and asked that we hire two meticulous temps during busy season, who I would personally train, so all the rest of us who were working our butts off and frequently sleeping under our desks could focus on tax return preparation instead of photocopying. The response was, "that's a wonderful idea, but 3 people before you have tried the same thing to no avail." I'm not willing to waste my life working for a company that isn't willing to accept the gift of productivity improvement from it's employees. I found a job within 2 weeks and was gone.