Vista has a long history of problems with AV programs, and it appears Avast is the latest victim.
Interesting. I'd restate this a little more broadly: "Programmers have a long history of thinking they know what they are doing, but usually they can't, don't, or won't test thoroughly to prove it. It appears that Avast programmers fall into this trap also."
I've used Vista Ultimate 32 bit on a laptop for well over a year now. I'm quite happy with the operating system and its performance. It seems to be resilient and resist problems fairly well, where XP would just hang. I suspect I pay a bit of performance penalty compared to XP, but that performance goes into a considerable amount of background monitoring of events and diagnostics that are relatively easy to find and interpret and that I never had with XP. I had a few driver issues early on with external devices, but those manufacturers caught up. The only serious problem I have had is with the Vista built in backup. It worked great for a while then stopped. I gave up on it and purchased a highly rated 3rd party product for $35 to solve that problem. I wish all my problems could be solved for only $35.
I use Avast because I have had poor experience with purchased A/V products. McAfee seems to be indistinguishable from adware, Symantec is prone to crashing the machine, TrendMicro seems to be leaky, Panda duns you with e-mails, etc. I'd pay for reliable, trouble-free A/V software that leaves me alone and does its job, but I haven't found it. I turned to free A/V software like Avast because it was highly rated and it irked me to pay for trouble with purchased A/V products.
Avast, amazingly, seemed to be both reliable and trouble-free, or at least it did until the 4.8 update. Since then, I have had recurring, intermittent problems. If I turn off Avast, the problems go away. If I turn it on, they recur. Vista has been out for a couple of years, 4.8 has been out for 2 weeks, and it seems pretty clear that the new problems I've been having in the past 2 weeks are Avast's, not Vista's.
My problems seem to be:
1) Sometimes, when I start up Outlook the first time after startup, I can't get Outlook to run normally. If I switch folders, there is an indefinite waiting period of several minutes before loading the folder seems to complete. If I restart, Outlook may or may not (but usually will) run properly. When Outlook runs slowly, if I halt Avast, close Outlook, and restart Outlook, Outlook works fine. If I restart Avast without rebooting, usually Outlook will run slowly again. I have a sense that there is some timing relationship between system start, Avast start, and Outlook start that has to be just right.
2) Sometimes web pages load very slowly. Sometimes it is certain web pages, sometimes it is every web page. If I stop Avast, then close and restart the browser, any pages that were previously slow will now load quickly. When I restart Avast, things seem to continue to run at the expected speed rather than becoming slow again. It's taken me a while to learn the trick, but now whenever my browser runs slowly, I turn off Avast.
This is not a criticism of the original post or the author. I used the opening quote because I don't want the spotlight to be redirected away from Avast (our dear friend) to Vista (a M$ product, therefore bad). I do think there is something that has changed for the worse in 4.8 and needs to be fixed. Everything I see tells me this is a problem with Avast and not with Vista. I like Avast and would like to see them fix the problem.