In the past few months I had 1 or 2-off experiences with all of the following:
UPS - Timely enough, but agree with others re: care taken by deliverers. One time (2 years ago) had package lost during holiday season and then had it turn up under an employee's UPS desk or something (corporate/mgmt people contacted me about it) .. and then had to go pick it up in person from local UPS warehouse.. and then had the contents of package fail pretty early in (though doubt can attribute that to UPS vs the product itself (a laptop)). Seems like they caught a seasonal employee stealing packages and recovered mine or something - total delay was about 2 weeks though. Another time more recently (5-6 months ago), had ordered some furniture and they delivered it to my neighbor across the street instead of to me. Carrying it across the street was kind of a PITA .. not a huge mess-up for my situation but could be for others.
FedEx - Only had experience with their International Priority shipping lately their ground service is TERRIBLE also (see edit below) but their priority shipping (which is bit more expensive than budget) is amazing; from the minute I ordered something from Korea, it was on my doorstep within 3 days (2 of which were weekends, so 1 business day; ordered Thursday evening at 10pm EST and on my doorstep 7am on Monday). Can't reason about their handling since the product wasn't fragile enough to assess for issues. A number of years ago I think I remember using their domestic/budget service (?) and that was not nearly as good, though (can't remember what/why; probably delays).
USPS - No issues, reliable & fast IMO.
DHL - The package got to me eventually but was delayed by 2 days (7 instead of 5), can't reason too much about handling though (speed copper switches in a plastic bag within cardboard box - maybe a few had bent pins, cardboard box largely in its original shape tho). I disliked DHL the most due to the delay(s) and lack of info as I kept refreshing the tracking page quite frequently. To be sure, other shippers had many delays as well, but they were on the retailer's side. Reflecting after having written this, I'd probably opt for DHL over UPS though; though I have never had DHL ship anything worth more than $50 to me so I can't really give an apples to apples comparison on their reliablity for such things..
Based on this, for shipping a keyboard (aka ~$300 product?), would say FedEx >= USPS >> UPS = DHL. Tho not sure - pls take others' opinions/experiences.
*EDIT*: I take this back, supposed to receive FedEx Ground package today - marked as delivered but not there (few minutes after marked delivery time) - probably delivered to wrong address (not direct neighbors). Agree though that all priority services >>> ground/economy services.