I went 2 years ago, so relatively recently, but I only had 2 weeks, so I just flew into Padang, headed up to Bukitinggi, Lake Maninjau and a little place I wanted to explore near Lubuk Sikaping.

Regards the Tsunami, not many people (bar Aussie surfers) really head up to Aceh where most of the damage was done.

If you have a good 2/3 weeks you could have an amazing trip (never forget how big Sumatra is, or how bad the basic transport infrastructure is!).

I've done this trip before - some wonderful memories.

Fly to Medan.
Spend a couple of days in Bukit Lawang Orang-Utan sanctuary.
Head to Berestagi (sp?) to climb a volcano, and drink some passion juice.
Head to Lake Toba for a few days marvelling just how stunning the place is - truly mindblowing.
Then - the nasty bit! - the trans-Sumatran highway for 8/10/12/14/24 hours (depending on road conditions!) to Bukitinggi (but I can recommend an en-route stopover that I have an interest in as a friend is building a small eco-lodge!).
Chill in Bukitinggi - really nice town, then head down to Lake Maninjau for further relaxing.
Finally, head to Padang, and fly out of Padang.

Yeh, just gets me happy thinking about it, happy times!