I have been all mac for trading since IB TWS went Java. I use Linnsoft for charting and quotes with DTNIQ feed. I have also used trendsetter's Pro TA which is a basic, inexpensive, though solid program that only works with the MyTrack feed.
The newer dual processor macs are fast enough to run windows emulation without too much of performance hit for any crucial programs which aren't on the mac. I haven't tried esignal in emulation but I did try the DTNIQ app. which seemed to run just fine. I would guess esignal works too.
OS X is solid as a rock with uptimes lasting for months and it is not even a tenth as squirly as win 2k. Highly recommended for trading if you can work with the available software, IMHO.