I purchased a Ledger Nano S over a year ago and have used it quite a bit. Here are my thoughts listed as Pros and Cons.

Pros:

(1) it is currently very inexpensive at around $60 mainly because it has been superceded by the Nano X which I think is compatible with mobile phones whereas the S needs to be used on PC. I stupidly paid over $100 for mine.

(2) If you are a HODLer (holding crypto for longer term) then it is the safest way to hold your crypto as holding on exchanges or project wallets tends to be riskier as most can be hacked and you are not guaranteed to be covered.

(3) Most but not all cryptos are compatible and many are aiming to become compatible e.g Electroneum ETN.

(4) It is reasonably easy to use once you get used to it (if you are familiar with crypto transfers etc).

Cons:

(1) You have to tranafer crypto to centralised exchanges to sell or if a decentralised exchange connect to your ledger from their site. This could result in losing opportunities where there are short term pumps of prices. 

(2) If you have a diverse set of cryptos in your portfolio you will probably have to keep adding and deleting the software for each on your ledger as it only has capacity to hold about 4 crypto apps at one time. E.g. there is bitcoin, ethereum, ripple Xrp, cardano, chainlink, icon, stellar lumens XLM etc but you cant have the software for these all on ledger at same time.

(3) You cant always stake your crypto to earn interest on the ledger. Some cryptos do allowing staking from your ledger.

In conclusion I would recomnend storing as much of your crypto as possible on your ledger and maybe keep a small amount on exchanges if you want to be able to trade. Then you will know your crypto is pretty much safe.