Feelings mixed ...
I was a long-time user of Adaptec's Easy CD Creator, from the 3.0 version that came bundled with my HP drive through 4 and 5. Roxio "spun off" from Adaptec, and the quality of the product plummetted. Easy CD Creator 5 was the root cause of massive instability on my Windows box for quite a while, and was nearly impossible to uninstall (I ended up reinstalling Windows). And I'm by far not the only one who's had instability from Roxio's recent offerings.
IMHO, Roxio has massive QC problems. I was astonished to see Microsoft outsource their CD writing to Roxio (and not all that surprised when XP's CD-writing software turned out to be buggy as hell on my equipment while the "unintegrated" Nero works swiftly, safely, and error-free). But, they make good business deals, and by hook or crook practically owned the PC CD-writing market for a few years (now Nero is gaining dominance and a few others get airplay).
I've never used Toast on my Mac, so I can't say what kind of quality Roxio puts into its Mac products. However, if Apple were to buy Roxio and didn't
immediately clean house on the Windows division, we'd see users blaming
Apple for their PC crashing.
Buggy software, no matter what its market share, is no calling card for switchers.
Add to that the Netscape brand and PressPlay contracts/back-end: Apple needs neither, as it has better name recognition, better contracts, and a more battle-tested and tuned back end. This can only be seen as a defensive play, keeping MS or the like from easy entry into competing with iTMS.
So, mixed feelings here. I don't see the advantage to Apple buying Roxio. But then, maybe that's why I don't have an MBA