PV Sol Expert is unstable. I made the mistake of purchasing PV Sol Expert this year and have had nothing but problems. It constantly crashes and I have wasted countless hours trying to sort out various problems. Their technical support in the UK is poor and you sense that there is no real depth of understanding. Expect them to have to get back to you rather than solve your problem, but then expect to have to chase them.
Designing with different complex building types is remarkably difficult and you can expect to while away hours trying to work our how to change some of the roof pitches correctly. Also don't expect them to share your frustration, they appear not to be paid per hour and will happily have you remove and reload your software over again.
Save your money and source another software programme, I sincerely wish I had. Polysun is highly rated.