There are two types of windows:
- A large one, which is intended to help you spot a boat on a collision course. That's a safety feature. If you are always the only boat on the lake, you might be able to get by without.
- A small one, which is situated right at the tell tales. It will let you view the leeward telltale. If you truly don't care how your sails are trimmed, that one is a waste, otherwise it's nice. My last sail came without and I miss it. The sail cloth is slightly translucent, so I can see the shadow of the leeward telltale, most of the time, but not when the sun is on the wrong side.
For reef points: these can be retrofitted, manually with a kit, or by any sailmaker for about $150.00 (modulo inflation). One of the first things I modified in my rigging was to add a reef. I sail in an area of mostly moderate winds, but every once in a while it picks up. It's not rare for this to be short term, so you are out on the water, and then a blow comes through for an hour and is gone again. I like to be able to put in a reef, so I can deal with situations like that in a more relaxed fashion, instead of having to miss the entire afternoon just because the max forecast is just a bit beyond of what would be comfortable with a full sail.
I have sailed some multi-day events on a DS in areas of stronger winds and where you couldn't easily adjust your itinerary based on the forecast. In other words, the requirement changed to being able to handle what you'd find on the water (or break off the entire thing). Boats that entered usually had three reefs and some carried a storm jib as well.
There are a number of discussions here on reefing, putting in reef points, and so on. If you haven't, it's worthwhile to look around a bit (and not just in this section as some took place in other sections). There are also some mentions on techniques for putting in a reef, something we discussed quite recently in a post on rigging.
Anyway, I looked at what info I could find on the sails from DR and at the price they look like a good buy.
PS: I always assume that both cruisers and racers really want to get the best out of their sails. For cruisers it's not so much to get every last 1/10th of a knot of boat speed, but, for example, whether they can get around a headland or island without tacking, or how much progress can be made on a stretch where current and wind are against them. And finally, whether the sails can be trimmed flat enough when the wind picks up to be able to struggle less in gusts and delay a bit the need to put in a reef or even take down the sails.