I've been selling on eBay since 1999, and using TP since they came out. Two or three year ago, TP was the way to go because they had great data back 90 days or more and ebay was offering just 14 days in completed auctions. Now ebay is offering much better completed auction data, and many way to sort it.
If you are trying to figure out what something is worth on ebay, you can't do much better than the do a completed ebay sale search and sort by recent sales first. You will immediately see what you can sell it for today. If you are after business intelligence, who the sellers are in your category etc, then TP is still the best way to go.