hi garfield
we went to nepal for our honeymoon and visited two places - kathmandu and pokhara where the annapurna ranges are. It was definitely an insight, we learnt a lot abt their culture and how the nepalis lived but at the same time, a definite culture shock.
Kathmandu is generally chaotic, esp within the city of Thamel where most tourists stay - it's pretty polluted, no road regulations and half the time shopkeepers are cajoling you to go in or buy something. There are many shops and fun knick knacks if you enjoy shopping.. although it can get very stressful walking ard the area.
Sights to see, temples, temples and temples (Swayambhunath or Monkey Temple, Bodhnath Stupa). There's also the Pashupatinath temple which is located by the Bagmati River where they have open cremations. Go to Durbar Sq in Kathmandu itself. You can also take a walk around the ancient cities of Patan and Bhaktapur.
If you have time, you might want to spend one or two nights at Nagarkot. We only went up for a few hours and regretted not knowing abt the place earlier. It's the highest point where you can get a good view of the Everest ranges (incl a little bit of Mt Everest). It's also a very peaceful and serene area where you can overlook Kathmandu city.
The 6 hour bus ride north-west to Pokhara is definitely worth it. There, you get a clear view of the Annapurna ranges. You can spend a few days there to relax by the lake as well. You can hike up the hills of Sarangkot to have a fantastic view of the ranges.
Another place where i did not get to go, but was highly recommended was the Royal Chitwan National Park. There, you get to see the wildlife up close in their safari.
Nepal is not what you call a typical honeymoon. You have to be prepared that their standard of living is totally different from back home. So you've gotta be prepared to 'rough it out' there and don't be surprised if things don't always work there. Their 3-star hotels is a whole different classification from our 3-star hotels. But if you don't mind all these, Nepal is good fun
We went in Oct and according to the travel guides, Oct and Nov is the best time to go there because it's after the monsoon season. Weather there is generally cooling - unless there's the sun. So it's warm/hot in the day, cool/cold when there's no sun. Bring sunblock tho! I didn't, and ended up getting an uneven tan because i was hiking in my short-sleeved t-shirt. heehee.
I will recommend that you pick up a copy of the Lonely Planet as it'll definitely come in handy