I have a 5021, and haven't experienced that problem. The 5020's run within normal Acer temperatures, compared to the 8200's and Ferrari's.
At the same time, I do think that the 5020's have stopped production a while back. It's a solid computer, but in the time since it's come out, and I've bought mine, honestly there are many new options to choose from. There's the 4400 and several AMD options from other brands.
Also, the Intel core duo's are out and while they lack 64bit, it may be highly possible to get a cpu later. Merom, the 64bit consumer Pentium M followup, supposedly fits the Yonah socket too.
"Word reaches the Deeplung ear that Intel's Yonah processor, which ships under the Intel Core Duo moniker, has features that aren't being exposed to the consumer. Intel's Sossaman is the key, and Sossaman is the codename for an ultra low voltage Yonah to be shipped under the Xeon brand, into the server and workstation space.
And it transpires that Sossaman supports iAMD64, er, sorry, 'EM64T', symmetric multi-processing with another Sossaman Xeon, and hardware virtualisation. Intel's implementation of the 64-bit extension to x86, SMP and hardware VT are all missing from the official specs of Intel Core Duo consumer processors, despite Yonah and Sossaman being the same thing. "http://www.hexus.net/content/item.php?item=4604
A laptop is a relatively big investment, so take your time and weigh out the pros and cons. I just don't want you to get a laptop and then 3 days later feel like you made the wrong decision.
Hope you find what you want