Gouves is quite spread out with 2 distinct parts. To the west, there is a quite large sandy beach near the furthest west of the 2 harbours, which are within 200m of each other. From the eastern harbour there is a road leading up to the main street, where there are shops, restaurants and a few bars. It is not a night club type of resort.
There is a dive centre (Big Blue) in between the 2 harbours, however when we were there in August 2011 it appeared to be closed. Looking at TA reviews, the most recent one also states that it is no longer operating. Who knows if it will be around this year - probably not. Anyway, the details are here:
Apart from Big Blue, you can see from this site that the next nearest one to Gouves is in Hersonnisos.
If you walk along the coast eastwards from the harbour, there is a rocky shore with no beach to speak of until you get to a small chapel on a headland (about 800m). After that, there is a small rocky beach, good for snorkelling, then after that are 2 lovely sandy coves. The first one is about 100m across, the second one about 200m, then there is a further less attractive beach, but with lots of rock pools near the shoreline which can be quite interesting.
Near the 2 coves there is quite a lot of accommodation, tavernas and restaurants, including 2 of the best tavernas we have ever been to in Greece - Philipos and Skorpios. Behind the Island hotel there is a street with several restaurants, shops, supermakets, car hire etc.
The 2 coves are really nice for sunbathing and swimming, with a couple of bars and supermarkets close by for refreshments!
Gouves is ideally located for excursions by car - or bus for that matter. Nowhere is more than about 10 minutes walk from the main road, where you can get a bus to Heraklion or Hersonnisos/Malia/Ag. Nikolaos. Gouves is pretty central on the island, which means that with a car you can get more or less everywhere except the furthest southern coasts on a day trip. There is a fast road all along the north coast from Ag. Nik past Heraklion, Rethymnon and Chania to Kissamos in the west, which makes things quite easy. However, distances can be quite large as Crete is of course a very large island.
Gouves does most things pretty well - it is close to the airport for an easy transfer, is good to use as base for travelling round, has some good beaches, good tavernas, enough shops etc.
Hope this helps, if you need any more detailed info come back and ask.