It seems that people mostly receive window envelopes from companies such as banks, credit card companies, and people who send junk mail. Is there a reason why us regular people don't sue window envelopes more often? They do, afterall, seem to be quite professional and save you from having to write the person's address on the front of the envelope!
I personally haven't started using window envelopes myself but it is something I am considering trying in the near future. Of course, I have to use up my last 50-pack of regular/plain envelopes. Given that I don't send a ton of mail in any given week this may take longer than I expect.
In other news, I finally found a good source of small padded mailing envelopes again. The store I regularly get them from hasn't carried them in at least six months which is unfortunate because they had great deals on them. I didn't like having to buy them one by one from the post office (at at least 4x the cost overall compared to buying them in bulk). I actually bought 30 these cheaper padded envelopes today to stock up!